From: Yann Collet <cyan@fb.com>
Date: Tue, 22 Oct 2024 22:25:45 +0000 (-0700)
Subject: conservatively estimate over-splitting in presence of incompressible loss
X-Git-Tag: v1.5.7^2~71^2~14
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ea85dc7af6f97cbfc7fd1e6ff1515660e58501a3;p=thirdparty%2Fzstd.git

conservatively estimate over-splitting in presence of incompressible loss

ensure data can never be expanded by more than 3 bytes per full block.
---

diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index edb71ae50..85966d888 100644
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -4587,6 +4587,7 @@ static size_t ZSTD_compress_frameChunk(ZSTD_CCtx* cctx,
             }  /* if (ZSTD_useTargetCBlockSize(&cctx->appliedParams))*/
 
             if (cSize < blockSize) savings += (blockSize - cSize);
+            else if (savings) savings--;
             ip += blockSize;
             assert(remaining >= blockSize);
             remaining -= blockSize;